<template>
  <div class="spec-preview">
    <img :src="currentImg?.imgUrl" />
    <div class="event"
    ref="eventRef"
    @mouseenter="isShow = true"
    @mouseleave="isShow = false"
    @mousemove="moveHandler"
    ></div>
    <div class="big" v-show="isShow">
      <img :src="currentImg?.imgUrl" 
      ref="bigRef"
      />
    </div>
    <div class="mask" v-show="isShow"
    ref="maskRef"></div>
  </div>
</template>

<script>
  export default {
    name: "Zoom",
    props: ['skuImageList'],
    data() {
      return {
        isShow : false,
        index: 0
        }
    },
    computed: {
      currentImg() {
        return this.skuImageList[this.index]
      }
    },
    mounted() {
      this.$bus.$on('changeIndex',this.changeIndex)
    },
    methods: {
      changeIndex(index) {
        this.index = index
      },
      moveHandler(e) {
        //start拿到鼠标起始位置
        let startX = e.offsetX
        let startY = e.offsetY
      
      // 计算蒙版左上角位置
      let endX = startX - this.$refs.maskRef.clientWidth / 2
      let endY = startY - this.$refs.maskRef.clientHeight / 2
      
      //水平方向边界判断
      if (endX < 0){
        endX = 0
      }
      if (endX > this.$refs.eventRef.clientWidth - this.$refs.maskRef.clientWidth ) {
        endX = this.$refs.eventRef.clientWidth - this.$refs.maskRef.clientWidth
      }
      //垂直方向边界判断
      if (endY < 0) {
        endY = 0
      }
      if (endY > this.$refs.eventRef.clientHeight - this.$refs.maskRef.clientHeight) {
        endY = this.$refs.eventRef.clientHeight - this.$refs.maskRef.clientHeight
      }

      this.$refs.maskRef.style.left = endX + 'px'
      this.$refs.maskRef.style.top = endY + 'px'

      this.$refs.bigRef.style.left = -2 * endX + 'px'
      this.$refs.bigRef.style.top = -2 * endY + 'px'
      }
    }
  }
</script>

<style lang="less">
  .spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
      width: 100%;
      height: 100%;
    }

    .event {
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 998;
    }

    .mask {
      width: 50%;
      height: 50%;
      background-color: rgba(0, 255, 0, 0.3);
      position: absolute;
      left: 0;
      top: 0;
      // display: none;
    }

    .big {
      width: 100%;
      height: 100%;
      position: absolute;
      top: -1px;
      left: 100%;
      border: 1px solid #aaa;
      overflow: hidden;
      z-index: 998;
      // display: none;
      background: white;

      img {
        width: 200%;
        max-width: 200%;
        height: 200%;
        position: absolute;
        left: 0;
        top: 0;
      }
    }

    // .event:hover~.mask,
    // .event:hover~.big {
    //   display: block;
    // }
  }
</style>